INVESTMENT SECURITIES, Investment Securities in a Continuous Unrealized Loss Position (Details)	Jun. 30, 2020 USD ($) Position	Dec. 31, 2019 USD ($) Position
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	219	88
12 months or longer | Position	3	62
Total | Position	222	150
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 124,839,000	$ 710,602,000
12 months or longer	15,000	83,378,000
Total	124,854,000	793,980,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	292,000	8,351,000
12 months or longer	0	789,000
Total	$ 292,000	$ 9,140,000
Equity and Other Securities, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	1
12 months or longer | Position	0
Total | Position	1
Equity and Other Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 79,000
12 months or longer	0
Total	79,000
Equity and Other Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	22,000
12 months or longer	0
Total	22,000
Available-for-sale, allowance for credit losses	$ 0
U.S. Treasury and Agency Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	8	12
12 months or longer | Position	0	5
Total | Position	8	17
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 12,058,000	$ 592,678,000
12 months or longer	0	25,998,000
Total	12,058,000	618,676,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	18,000	7,970,000
12 months or longer	0	5,000
Total	$ 18,000	$ 7,975,000
Obligations of State and Political Subdivisions [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	52	21
12 months or longer | Position	0	0
Total | Position	52	21
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 20,145,000	$ 22,716,000
12 months or longer	0	0
Total	20,145,000	22,716,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	20,000	26,000
12 months or longer	0	0
Total	$ 20,000	$ 26,000
Government Agency Mortgage-Backed Securities [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	142	50
12 months or longer | Position	2	52
Total | Position	144	102
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 87,290,000	$ 89,237,000
12 months or longer	15,000	52,975,000
Total	87,305,000	142,212,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	248,000	341,000
12 months or longer	0	766,000
Total	$ 248,000	$ 1,107,000
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-Sale Portfolio in Unrealized Loss Positions, Number of Positions [Abstract]
Less than 12 months | Position	17	5
12 months or longer | Position	1	5
Total | Position	18	10
Available-for-Sale Securities, in Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 5,346,000	$ 5,971,000
12 months or longer	0	4,405,000
Total	5,346,000	10,376,000
Available-for-Sale Portfolio, Debt Maturities, Gross Unrealized Losses [Abstract]
Less than 12 months	6,000	14,000
12 months or longer	0	18,000
Total	$ 6,000	$ 32,000
Equity Securities, at Fair Value [Member]
Equity and Other Securities, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Less than 12 months | Position	1
12 months or longer | Position	0
Total | Position	1
Equity and Other Securities, Continuous Unrealized Loss Position, Fair Value [Abstract]
Less than 12 months	$ 79,000
12 months or longer	0
Total	79,000
Equity and Other Securities, Continuous Unrealized Loss Position, Gross Unrealized Losses [Abstract]
Less than 12 months	22,000
12 months or longer	0
Total	$ 22,000